Increase In Rice Grain Yield Research Articles

Hydrothermal carbonization of biogas slurry and cattle manure into soil conditioner mitigates ammonia volatilization from paddy soil

Hydrothermal carbonization of biogas slurry and animal manure into hydrochar could enhance waste recycling waste and minimize ammonia (NH3) volatilization from paddy fields. In this study, cattle manure-derived hydrochar prepared in the presence of Milli-Q water (CMWH) and biogas slurry (CMBSH), and biogas slurry-based hydrochar embedded with zeolite (ZHC) were applied to rice-paddy soil. The results demonstrated that CMBSH and ZHC treatments could significantly mitigate the cumulative NH3 volatilization and yield-scale NH3 volatilization by 27.9–45.2% and 28.5−45.4%, respectively, compared to the control group (without hydrochar addition), and significantly correlated with pH and ammonium–nitrogen (NH4+–N) concentration in floodwater. Nitrogen (N) loss via NH3 volatilization in the control group accounted for 24.9% of the applied N fertilizer, whereas CMBSH- and ZHC-amended treatments accounted for 13.6−17.9% of N in applied fertilizer. The reduced N loss improved soil N retention and availability for rice; consequently, grain N content significantly increased by 6.5–14.9% and N-use efficiency increased by 6.4–16.0% (P < 0.05), respectively. Based on linear fitting results, NH3 volatilization mitigation resulted from lower pH and NH4+–N concentration in floodwater that resulted from the acidic property and specific surface area of hydrochar treatments. Moreover, NH3-oxidizing archaea abundance in hydrochar-treated soil decreased by 40.9–46.9% in response to CMBSH and ZHC treatments, potentially suppressing NH4+–N transformation into nitrate and improving soil NH4+–N retention capacity. To date, this study applied biogas slurry-based hydrochar into paddy soil for the first time and demonstrated that ZHC significantly mitigated NH3 and increased N content. Overall, this study proposes an environmental-friendly strategy to recycle the wastes, biogas slurry, to the paddy fields to mitigate NH3 volatilization and increase grain yield of rice.

Long-term manure application increased soil organic carbon and nitrogen mineralization through accumulation of unprotected and physically protected carbon fractions

Soil organic carbon (SOC) and nitrogen (N) mineralization are important biogeochemical processes associated with soil fertility. These processes are influenced by physically, chemically, and biologically stabilized organic carbon (C) fractions, the mechanisms of which are not well-known. The present study was conducted to evaluate the combined effect of manure and mineral fertilizers on the content of C fractions to promote the mineralization of SOC and N. Treatments included: i) unfertilized control (CK), ii) a combination of nitrogen, phosphorus, and potassium (NPK), iii) manure (M), iv) manure combined with NPK (MNPK), and v) a high dose of manure combined with NPK (hMNPK). The combined use of manure and mineral fertilizers enhanced accumulation of the unprotected C fraction (cPOC) by 44-72% compared to the CK. Manure application enhanced physical (µagg), physico-chemical (H-µsilt), and physico-biochemical C (NH-µsilt) fractions by 30-56%, 62-150%, and 27-51%, respectively. In contrast, chemically and biochemically protected fractions showed a minor response to manure application. Accumulation of cPOC, C in microaggregates (µagg), and physico-chemically protected C fractions (H-µsilt and H-µclay) significantly contributed to the mineralization of SOC and N, resulting in a significant increase in rice grain yield with long-term manure additions. In summary, long-term use of manure and mineral fertilizers improved soil C accumulation in unprotected and physically protected fractions, which enhanced SOC and N mineralization and benefited soil productivity in a rice-wheat cropping system.

Integrated management of gundhi bug (Leptocorisa spp.) infesting aromatic rice

The field trial conducted at Rice Research Farm of Birsa Agricultural University, Ranchi during Kharif season of 2018 and 2019 with aromatic rice variety Birsa Vikas Sugandh-1 revealed that three foliar sprayings applied at 25,55 and 85 days after transplanting with tipronu 5SC @ 1200 ml ha-1 recorded lowest mean gundhi bug population (1.96) and highest polled mean yield (47.17 q ha-1) followed by 2.9 and 46.13 q ha-1, respectively recorded with fipronil 5SC @ 1000 ml ha-1. Fipronil @ 1200 ml ha-1 recorded increased grain yield of 29.04 q ha-1 over the control. Alternate spray of fipronil and botanical insecticide neem (2.5 l ha-1) also recorded appreciable reduction in gundhi bug population (4.21) and 23.5 per cent increase in rice grain yield over the control.

The Elite Alleles of OsSPL4 Regulate Grain Size and Increase Grain Yield in Rice

Grain weight and grain number, the two important yield traits, are mainly determined by grain size and panicle architecture in rice. Herein, we report the identification and functional analysis of OsSPL4 in panicle and grain development of rice. Using CRISPR/Cas9 system, two elite alleles of OsSPL4 were obtained, which exhibited an increasing number of grains per panicle and grain size, resulting in increase of rice yield. Cytological analysis showed that OsSPL4 could regulate spikelet development by promoting cell division. The results of RNA-seq and qRT-PCR validations also demonstrated that several MADS-box and cell-cycle genes were up-regulated in the mutation lines. Co-expression network revealed that many yield-related genes were involved in the regulation network of OsSPL4. In addition, OsSPL4 could be cleaved by the osa-miR156 in vivo, and the OsmiR156-OsSPL4 module might regulate the grain size in rice. Further analysis indicated that the large-grain allele of OsSPL4 in indica rice might introgress from aus varieties under artificial selection. Taken together, our findings suggested that OsSPL4 could be as a key regulator of grain size by acting on cell division control and provided a strategy for panicle architecture and grain size modification for yield improvement in rice.

Effects of biochar on methane emission, grain yield, and soil in rice cultivation in Thailand

Biochar has been recommended as a soil amendment to improve soil fertility and mitigate methane (CH4) emissions from rice cultivation. Its effects, however, vary depending on soil type, biochar characteristics, and application rate. This study was aimed to evaluate the potential of mangrove biochar on CH4 mitigation, soil properties, and the productivity of rice cultivated in a clay loam soil in Thailand. Biochar was used at a rate equivalent to 10 t ha−1 season−1, both with (biochar + fertilizer: BF) and without (biochar alone: BI) fertilizer, for two cultivation seasons. BI reduced CH4 flux at most stages of rice growth. Relative to control soil (no biochar, no fertilizer: CT), BI significantly decreased cumulative CH4 emissions by 21.1% in the first season and 24.9% in the second season. CH4 emissions from BF soil were also less than those from the use of fertilizer alone (FE). Rice grain yield in BI was 7.85% and 14.4% greater than in CT, and in BF by 1.47% and 3.72% greater than FE, in the first and second seasons, respectively. The decrease in CH4 emissions and increase in rice grain yield decreased CH4 emission intensity under biochar treatments. Soil pH, organic carbon, cation exchange capacity, and available nutrients in the soil increased with biochar addition. The soil organic carbon stock was significantly increased by 32.6% in BI and 27.5% in BF after the first season, and by 43.5% in BI and 39.6% in BF after the second season.

Crop and Residue Management Improves Productivity and Profitability of Rice–Maize System in Salt-Affected Rainfed Lowlands of East India

This study was conducted over 3 years in a salt-affected coastal rainfed lowland ecosystem. Farmers most commonly grow tall rice varieties in the wet season to cope with flash and/or stagnant floods, leading to large amounts of rice residue production. Most of the land remains fallow during the dry season because of increased salinity and scarcity of freshwater for irrigation. The study aims to provide options for increasing cropping intensity through management of crop residues (CR) and soil salinity, conservation of soil moisture, and reduction in production cost. The rice–maize rotation was assessed with rice as the main plot as (1) puddled transplanted rice (PTR) with CR of both rice and maize removed, (2) PTR and 40% CR of both crops retained, (3) dry direct-seeded rice (DSR) with CR of both crops removed, and (4) DSR with 40% CR of both crops retained. Maize in the dry season was supplied with different N levels as sub-plots—control (0 kg N ha−1), 80, 120, and 160 kg N ha−1. DSR, when combined with CR retention (DSR + R), reduced soil salinity. The increase in rice grain yield with CR retention (observed in second and third years) and crop establishment (higher in DSR versus PTR in the third year) was 16 and 24%, respectively. The cost of production increased by 17% (USD 605 ha−1) in PTR compared with DSR (USD 518 ha−1). CR retention reduced irrigation water requirement by 37% and N requirement by 40 kg ha−1 for hybrid maize. When CR was removed (−R), the N requirement for hybrid maize increased to 160 kg N ha−1 compared to when it was partially (40%) retained, where the requirement was 120 kg ha−1 with similar yields. Available N was highest under DSR + R (314 kg ha−1) and lowest under PTR − R (169 kg ha−1), and it also increased with increasing N application up to 120 kg ha−1 (+R) and 160 kg ha−1 (−R). The results of the study hold promise for increasing cropping intensity and farmers’ incomes, with broader implications for increasing productivity on about 2.95 million hectares currently under a rice–fallow system in eastern India, and in coastal areas affected by similar conditions in South and Southeast Asia.

Improved grain yield and lowered arsenic accumulation in rice plants by inoculation with arsenite-oxidizing Achromobacter xylosoxidans GD03

Arsenite is the predominant arsenic species in flooded paddy soil, and arsenite bioaccumulation in rice grains has been identified as a major problem in many Asian countries. Lowering arsenite level in rice plants and grain via accelerating arsenite oxidation is a potential strategy to help populations, who depended on rice consumption, to reduce the internal exposure level of arsenic. We herein isolated a strain, Achromobacter xylosoxidans GD03, with the high arsenite-oxidizing ability and plant growth-promoting traits. We observed that arsenite exposure could promote A. xylosoxidans GD03 to excrete indole-3-acetic acid and thus promoted rice growth. The pot culture experiments of Indica rice cultivar Guang You Ming 118 (GYM118) demonstrated that A. xylosoxidans GD03 inoculation of paddy soil (4.5–180 × 108 CFU GD03/kg soil) significantly accelerated arsenite oxidation in flooded soil. The daily arsenic oxidation rate with GD03 inoculation was 1.5–3.3 times as that without strain GD03 inoculation within the whole growth period of Indica GYM118 in the presence of the native microflora. It thus led to a 34–69%, 43–74%, 24–76% and 35–57% decrease in arsenite concentration of the stems, leaves, bran and grain of Indica GYM118 respectively and a 59–96% increase in rice grain yield. The paddy soil inoculated with 40.0 mL/kg of A. xylosoxidans GD03 resulted in a lowest As(III) concentrations in all rice organs of Indica GYM118, which equivalent to only 24–50% of the As(III) concentrations in the group without GD03 inoculation. The results highlight that a highly arsenite-oxidizing bacterium could accelerate arsenite oxidation of paddy soil when facing competition with the native microflora, thus decrease arsenic toxicity and bioavailable soil arsenic.

A quantitative trait locus GW6 controls rice grain size and yield through the gibberellin pathway.

Grain size is one of the essential components determining rice yield and is a target for both domestication and artificial breeding. Gibberellins (GAs) are diterpenoid phytohormones that influence diverse aspects of plant growth and development. Several quantitative trait loci (QTLs) have been identified that control grain size through phytohormone regulation. However, little is known about the role of GAs in the control of grain size. Here we report the cloning and characterization of a QTL, GW6 (GRAIN WIDTH 6), which encodes a GA-regulated GAST family protein and positively regulates grain width and weight. GW6 is highly expressed in the young panicle and increases grain width by promoting cell expansion in the spikelet hull. Knockout of GW6 exhibits reduced grain size and weight, whereas overexpression of GW6 results in increased grain size and weight. GW6 is induced by GA and its knockout downregulates the expression of GA biosynthesis genes and decreases GA content in the young panicle. We found that a natural variation in the cis element CAAT-box in the promoter of GW6 is associated with its expression level and grain width and weight. Furthermore, introduction of GW6 to Oryza indica variety HJX74 can lead to a 10.44% increase in rice grain yield, indicating that GW6 has great potential to improve grain yield in rice.

Improving soil silicon and selected fertility status for rice production through rice-mill waste application in lowland sawah rice field of southeastern Nigeria

PurposeRice-mill wastes are generated in large amounts in Ishiagu, Ebonyi State, Nigeria. These wastes can potentially be utilized for rice production and in improving soil attributes. This study evaluated the effects of rice-mill wastes on soil chemical properties and rice yield in sawah rice management.MethodsA sawah rice field in an inland valley of southeastern Nigeria was used in 2014 and 2015 cropping seasons for the study. Sawah refers to an Indo-Malaysian term for rice paddy. It involves the manipulation of some soil physical properties in form of ecological engineering works, by bunding, puddling and leveling of lowland rice field for water control and management. Two rice-mill wastes [rice husk ash (RHA) and rice husk dust (RHD) applied at 0, 2.5, 5, 7.5, 10 and 12.5 t ha−1] and the control were built into a split-plot in a randomized complete block design with three replications.ResultsBio-waste application had significant (p < 0.05) improved effects on the soil organic carbon, available P, soil available Si and total N compared with the unamended (control) treatment. There was significant (p < 0.05) increase in rice grain yield from 5.05 to 5.80 t ha−1 (for RHA) and 6.17–6.96 t/ha (for RHD) compared with 2.35–2.8 t ha−1 (control treatment) in both cropping seasons.ConclusionRHD and RHA treatments had significantly higher rice grain yield compared with the control treatment. Overall, rice grain yield was higher under RHD treatment compared with RHA treatment. This result demonstrated that RHA and RHD are potential agricultural resource for rice production in the study area.

Implementing the systems approach in rice pest management : India context

A basic IPM module for basmati rice as a part of integrated crop management accounting the pest prevalence and the information available from literature has been developed. As the module is location specific and dynamic, therefore needs regular updating and fine tuning depending on the location and pest prevalence. The technology has been successfully validated and implemented during 1998 to 2019 in Pusa Basmati 1, Taraori Basmati, Dehraduni Basmati, Pusa Basmati 1121 in Haryana, Uttar Pradesh and Uttarakhand with little modification and fine tuning. Implementation of the technology resulted in increase in rice grain yield i.e., 21.6% in Pusa Basmati 1 at Shikohpur, in Uttar Pradesh 21.5% in Taraori Basmati at Chhajpur in Haryana, 19.5% in Type 3 in Uttarakhand, 14.5 to 22.7% in Pusa Basmati 1121 in Haryana and 38.2% in Pusa Basmati 1121 in Uttar Pradesh over farmer's practices (FP). In all the basmati rice trials, higher yield as well as Benefit - Cost (B-C) ratio was obtained in IPM as compared to FP. Implementation of IPM led to significant reduction in uses of chemical pesticides. In case of IPM, only 1.46 application of chemical pesticides (103.2 g a.i./ha) were undertaken in Pusa Basmati 1121 against 2.8 application in FP (1214.4 g a.i./ha) at Bambawad, Uttar Pradesh. ICAR-NRRI, Cuttack developed and validated IPM module at Sigmapur (Cuttack, Odisha) non-Basmati rice variety Pooja for four kharif seasons i.e 2010-2013 using standard agronomic practices. The trial resulted in an enhancement of 47.1% yield and 26.47 % B-C ratio over FP. Additional income of Rs. 9857/- per ha was also obtained in IPM over FP. On-Farm trial on validation of IPM module in non-Basmati rice (Pooja variety) under semi deep water conditions conducted in 10 ha during rabi 2017 at Nagapur and Basudeipur villages in Khurda district of Odisha resulted in reduction in the incidence of insect pests and diseases with higher population of natural enemies as compared to FP. Rice yield was recorded 5600 kg ha-1 in IPM as against 4900 kg ha-1 in FP. Recently, ICT based e-pest monitoring and advisory has become an important component for area wise implementation of IPM at state and national level. The programme has been successfully implemented in Odisha during 2010 and 2011 under RKVY. Implementation of the programme had resulted successful management of swarming caterpillar in 13 rice growing districts of Odisha during kharif 2010 and 2011.

Implementing the systems approach in rice pest management : India context

A basic IPM module for basmati rice as a part of integrated crop management accounting the pest prevalence and the information available from literature has been developed. As the module is location specific and dynamic, therefore needs regular updating and fine tuning depending on the location and pest prevalence. The technology has been successfully validated and implemented during 1998 to 2019 in Pusa Basmati 1, Taraori Basmati, Dehraduni Basmati, Pusa Basmati 1121 in Haryana, Uttar Pradesh and Uttarakhand with little modification and fine tuning. Implementation of the technology resulted in increase in rice grain yield i.e., 21.6% in Pusa Basmati 1 at Shikohpur, in Uttar Pradesh 21.5% in Taraori Basmati at Chhajpur in Haryana, 19.5% in Type 3 in Uttarakhand, 14.5 to 22.7% in Pusa Basmati 1121 in Haryana and 38.2% in Pusa Basmati 1121 in Uttar Pradesh over farmer's practices (FP). In all the basmati rice trials, higher yield as well as Benefit - Cost (B-C) ratio was obtained in IPM as compared to FP. Implementation of IPM led to significant reduction in uses of chemical pesticides. In case of IPM, only 1.46 application of chemical pesticides (103.2 g a.i./ha) were undertaken in Pusa Basmati 1121 against 2.8 application in FP (1214.4 g a.i./ha) at Bambawad, Uttar Pradesh. ICAR-NRRI, Cuttack developed and validated IPM module at Sigmapur (Cuttack, Odisha) non-Basmati rice variety Pooja for four kharif seasons i.e 2010-2013 using standard agronomic practices. The trial resulted in an enhancement of 47.1% yield and 26.47 % B-C ratio over FP. Additional income of Rs. 9857/- per ha was also obtained in IPM over FP. On-Farm trial on validation of IPM module in non-Basmati rice (Pooja variety) under semi deep water conditions conducted in 10 ha during rabi 2017 at Nagapur and Basudeipur villages in Khurda district of Odisha resulted in reduction in the incidence of insect pests and diseases with higher population of natural enemies as compared to FP. Rice yield was recorded 5600 kg ha-1 in IPM as against 4900 kg ha-1 in FP. Recently, ICT based e-pest monitoring and advisory has become an important component for area wise implementation of IPM at state and national level. The programme has been successfully implemented in Odisha during 2010 and 2011 under RKVY. Implementation of the programme had resulted successful management of swarming caterpillar in 13 rice growing districts of Odisha during kharif 2010 and 2011.

Effect of Rice Cultivars and Herbicidal Combinations Integrations on Weeds and Yield of Broadcast-Seeded Rice Productivity and Economic Feasibility

Nowadays there was an attitude from farmers to grow broadcasted seeded rice as an alternative to transplanted rice due to the scarce and costly labors in rice transplanting, but broadcasted seeded rice suffer severely from weed competition where sometimes the yield was sometimes completely lost. Finding good weed control package in rice fields which consist from. Main findings show that the use of old and newly herbicide molecules combination can succeed for sowing and rice broadcasted rice without problem. For these reasons two field experiments were conducted in split plot design were carried out at the Farm of Sakha Agricultural Research Station, Sakha, Kafrelshiekh , Governorate, Egypt during 2016 and 2017 summer seasons to evaluate the effect of two rice cultivars allocated as in the main plots two broadcasted seeded rice cultivars Sakha 106 and Sakha 104 were used in this study and thirteen weed control treatments which were the use of single herbicides or their combinations assigned in sub plots namely; Nominee at the rate of 800 cm/faddan, Saturn at the rate of 2 L faddan, Sirius at the rate of 80g/faddan, Basagran at the rate of 1.5 L/ faddan, Inpul at the rate of 20g/ faddan, Nominee at the rate of 800 cm L/faddan, followed by Basagran at the rate of 1.5 L/faddan, Nominee at the rate of 800cm /faddan followed by Sirius at the rate of 80g/faddan, Nominee at the rate of 800 cm/faddan followed by Inpul at the rate of 20g/ fed, Saturn at the rate of 2 L/faddan followed by Sirius at the rate of 80gfaddan, Saturn at the rate of 2 L/faddan followed by Basagran at the rate of 1.5 L/ faddan, Saturn at the rate of 2 L/faddan , followed by Inpul at the rate of 20g/faddan, hand weeding twice at 30 and 45 days and untreated check in each experiment on weeds, rice grain yield and its components as well as economic evaluation. Main finding results show that Sakha 106 cultivar had competiveness ability to weeds by good growth canopy and can participate by 24.9 & 25.0% weed suppression and increasing rice grain yield as tonnage per faddan by 10.55 & 15.09 % as compared with Sakha104 cultivar in both 2016 and 2017 seasons, respectively. This may be due that the vigorous growth of Sakha 106 cultivar which attributed to that cultivar more taller, more tillers and higher growth parameters to cover soil surface namely CGR,RGR and NAR which shed weeds and can combate with weeds than cultivar Sakha 104 conditions. On the other side the all used single herbicides or their combination succeeded to control weeds in rice yield by 37, 41 % and increasing grain yield as to tonnage per faddan by 1.398, 1.475 and exceeded hand weeding twice in two seasons, respectively. This may be due to the early elimination of weed competition and consequently improving rice all above rice growth parameters to utilize of natural resources of nutrients, light and space than untreated plots which heavily infested by weeds. The integration between both the role of rice cultivars and herbicides can maximize weed control and increase grain yield as tonnage per faddan than the use of single factor accompanied high incomes farmers. Application of inpul 20g /faddan+ Nominee 800 cm/faddan economical is considered as a good alternative to traditional weed control in broadcasted rice gave 82.9&84.% controlling of total weeds and increase in rice grain yield by 61.6 & 71.0% and exceeded hand weeding twice treatments as normal farmer practice for weed control in rice which gave 77.4 &77.7% weed control and increased grain yield 43.97 59.1 % in first and second seasons, respectively. Economic feasibility study of various studies weed management packages results referred clearly that under Kafrelshiekh condition by planting Sakha 106 cultivar with the use of any one of studied herbicides weed management is packages in broadcasted seeded rice and the best.

Dynamics of soil organic carbon mineralization and C fractions in paddy soil on application of rice husk biochar

Biochar plays a pivotal role in carbon storage-fractionation-mineralization process in soil. However, uncertainty still remains about the influence of biochar on these inter-related processes that links to C cycling in soil. A three years field experiment was initiated in 2013 at ICAR-National Rice Research Institute, Cuttack, India, to study the deviation in C mineralization and C fractions caused by the application of six doses of rice husk derived biochar (RHB), ranging from 0.5 t ha−1 to 10.0 t ha−1. The results showed an increase in cumulative CO2-C emission with increasing RHB rates. However, the model-fitted mineralization rates (dC/dt) did not show significant difference between treated and control soils at the end of incubation period in a laboratory study. In addition, microbial quotient and % C from RHB utilized showed a decreasing trend with increasing rates of RHB application, establishing the carbon sequestration potential of RHB. The highest rate (10.0 t ha−1) of RHB application accumulated maximum total organic C (3.26%) and a larger share of non-labile C (63.8%) among the treatments. An increase in rice grain yield (1–24%, depending on rate of RHB application) was observed with increasing rates of RHB which further established that RHB application not only enhanced C storage but also enhanced the productivity of rice by enhancing the soil fertility.

Plant growth promoting rhizobacteria suppress blast disease caused by Pyricularia oryzae and increase grain yield of rice

Plant growth promoting rhizobacteria are being widely utilized in agriculture due to their biopesticide and biofertilizer potential. The indigenous PGPR inhabiting certain hosts can act as potent bioinoculants due to their native habitat and acclimatization to the environment. Four hundred and fifty indigenous isolates were obtained from rice rhizosphere to assess their antagonism towards rice blast pathogen P. oryzae. Only 100 isolates showed antagonistic activity. Twenty out of 100 isolates inhibited the mycelium growth of P. oryzae by 30–65 % in vitro. Five strains, KFP-5, KFP-7, KFP-12, KFP-17 and KFP-18, showing 63–65 % antagonism towards P. oryzae, were tested for the production of biocontrol determinants and suppression of blast disease in rice plants. The antagonistic strains produced various biocontrol determinants such as the hydrolytic enzymes, protease, glucanase and cellulase with solubilization zone diameters of 10–19, 4.2–14.5 and 2–13.5 mm respectively and siderophores with zone diameter of 7–12 mm. The antagonistic strains also solubilized potassium, phosphorus and zinc from inorganic sources with solubilization zones of 2.1–3.2, 2.3–3.6 and 1.7-2.9 mm respectively. Three antagonistic strains, KFP-5, KFP-7 and KFP-17 significantly suppressed blast disease with a disease score 1.1–1.9 and increased yield of rice plants. The potent antagonistic strains were identified as members of the genus Bacillus by 16S rRNA gene sequencing.

Response of upland rice ‘Nerica-4 ’to rates of N and P fertilizers in south west Ethiopia

Decline in soil fertility is a major constraint in Abol Woreda of Gambella region of SW Ethiopia due to the continuous cropping, removal of crop residues after harvest, poor application of organic manures to soils, etc. The scientific information available concerning the response of upland ‘Nerica-4 ’rice variety to rates of N and P fertilizers in Gambella for its optimum productivity is limited. Therefore, a field experiment was carried out during 2014 cropping season at Abol Woreda, Gambella, South West Ethiopia to investigate optimum rates of N and P fertilizers for highest yield of rice (Oryza sativa L.). The treatments consisted of factorial combinations of four rates of N (0, 46, 92, and 138 kg N ha−1) and P (0, 23, 46, and 69 kg P ha −1) was laid out in a randomized complete block design (RCBD) with three replications. The effects of nitrogen were significantly (P = 0.05) different for harvest index, 1000-grain weight, plant height, panicle length, grain yield, straw yield, number of filled spikelets and unfilled spikelets, productive tillers, number of tillers and dry grain weight. On the other hand, many growth, yield, and yield components did not differ significantly (P > 0.05) due to application of P except number of unfilled spikelets, straw yield, and grain yield. Conversely, the interaction of N and P was significant (P = 0.01) for all yield and yield components except straw yield, harvest index and panicle length. Application of N and P significantly (P = 0.01) increased grain yield of rice up to the level of 92 kg N and 69 kg P ha−1. Highest grain yield (6.05 t ha−1) was obtained with the combined application of 92 kg N ha−1 and 69 kg P ha−1, and the yield advantage over the control was 113.7% (3.22 t ha−1). The economic analysis revealed that 92 kg N ha−1 with all rates of P (0, 23 and 46 kg) gave highest net benefits. Grain yield was significantly and positively correlated with straw yield (r = 0.66**), productive tillers (r = 0.423**), plant height (r = 0.632**), grain weight (r = 0.54**), panicle length (r = 0.453**), number of spikelets panicle−1 (r = 0.441**) and number of filled grain (r = 0.362**). This indicates that N and P increase grain yield of rice by positively affecting the important yield components. Therefore, it is inferred that farmers in the region can apply 92 kg N ha−1 with no phosphorus application to improve the grain yield of rain-fed Nerica-4 rice as well as for highest economic benefit.

Nitrogen use efficiency and yield of rice under different nitrogen and water stress conditions at grain-filling stage

以杂交籼稻"冈优527"和常规粳稻"农垦57"为材料, 设置硫酸铵(铵硝配比100∶0)、硝酸铵(铵硝配比50∶50)、硝酸钠(铵硝配比0∶100)3种形态氮肥及结实期4种水分胁迫处理[土壤水势(ψsoil)分别为0 kPa、 25 kPa、 50 kPa、 75 kPa, 持续处理14 d], 研究其对水稻氮素吸收利用及产量的影响。结果表明: 结实期土壤水势在 25 kPa时, 铵硝比50∶50处理较铵硝比100∶0处理的水稻籽粒产量增加显著, 铵态氮比例≥50%时, 适当增加硝态氮比例可缓解土壤水分严重不足对产量形成的不利影响。当土壤水势在0~ 25 kPa范围内适当增加硝态氮肥比例, 有利于促进稻株氮素累积, 尽管与纯铵态氮处理间未达到显著水平, 但与纯硝态氮处理间差异均达到显著水平。土壤水势≤ 50 kPa时, 增加硝态氮产量优势减弱, 相反增加铵态氮肥的比例更有利于产量形成。增加铵态氮有利于分蘖盛期前稻株对氮的吸收, 但在保证一定铵态氮比例下, 适当增加硝态氮有利于加快中、后期对氮素的吸收速度和氮素累积量, 为结实期氮素向籽粒转运及提高氮素利用效率提供保证。适度水分胁迫能促进结实期水稻对氮素的吸收, 促进结实期干物质累积, 提高各器官中营养物质向籽粒运转, 进而有利于收获指数的提高。杂交籼稻"冈优527"和常规粳稻"农垦57"对不同形态氮肥与结实期水分胁迫下氮素利用及产量的响应趋势基本一致。

Influence of Soil Amendments on Mitigating Methane Emissions and Sustaining Rice Productivity in Paddy Soil Ecosystems of Bangladesh

Two field experiments were conducted at two different rice ecosystems, one in the upland rice field of Bangladesh Agricultural University farm, Mymensingh and the another one in the low lying area of Bhaluka, Mymensingh to investigate the effects of soil amendments on mitigation of methane emissions and sustaining rice productivity. The experimental treatments were urea (250 kg ha-1), urea plus coal ash (1t ha-1), urea plus phosphogypsum (90 kg ha-1), urea plus silicate fertilizer (150 kg ha-1), ammonium sulphate 400 kg ha-1, ammonium sulphate plus silicate fertilizer (150 kg ha-1), urea (25% less than the recommended doze) plus cyanobacteria plus azolla (1t ha-1). In case of BAU upland rice field, the total seasonal CH4 emission was decreased by 12-21% and rice grain yield was increased by 4.0- 18.0% respectively, whereas 11.0-26.0% reduction in total CH4 emission and 4.5-24.0% increase in rice grain yield was recorded from the low lying rice field of Bhaluka with the application of soil amendments. Among the amendments silicate fertilization with urea and silicate in combination with ammonium sulphate reduced total CH4 flux by 18- 23% and 21-26% respectively, whereas rice grain yield was increased by 18-24% and 16-18%, respectively in both ecosystems. Although maximum reduction in total seasonal CH4 flux was recorded with silicate and sulfate of ammonia amendment in paddy soil, however soil acidity was developed which might affect soil fertility and rice productivity in the future. Therefore, silicate fertilizer could be introduced with the nitrogenous fertilizer sources, preferably with 50% urea plus 50% ammonium sulphate for reducing CH4 emissions and increasing rice productivity under both irrigated upland and lowland rice field ecosystems. DOI: http://dx.doi.org/10.3329/jesnr.v5i1.11574 J. Environ. Sci. &amp; Natural Resources, 5(1): 179 - 185, 2012

Improving the productivity of lowland soils for rice cultivation in Ghana: The role of the Sawah system

Lowlands constitute one of the largest and appropriate environments suitable for rice cultivation in Ghana. However, environmental degradation and declining soil productivity, leading to low crop yields are major concerns. Some reasons leading to such concerns may be traced to lack of proper management of our soil resources and possible unsuitable crop production systems and practices. Effective nutrient and water management in addition to suitable land preparation options are key factors for the effective and sustainable utilization of these inland valley ecosystems. Proper and meaningful management strategies therefore need to be developed in a way as to enable and encourage farmers to accept and easily adopt them. Designing and implementation of comprehensive and integrated soil management programs that will not only improve and maintain soil fertility but also make maximum use of available water are necessary. While research has shown that these environments vary considerably in soil type, water holding capacity and nutrient retention, it has been further observed that soils of most valleys are dominant in low activity clay minerals which have low nutrient and water holding capacities. Adoption of the “Sawah” system will enhance and sustain production. The Sawah system is characterized by nutrient replenishing mechanisms with intrinsic resistance to erosion (better water control and nutrient management). Rice responds better to fertilizer (mineral and organic) under the Sawah system than the traditional system of rice production in Ghana. Rice cultivation under the “Sawah” system in inland valleys in Ghana has lead to significant improvement in soil and water management. There has been a gradual and significant increase in rice grain yield in the order: farmers practice < only bunded < bunded and puddled < bunded, puddle and leveled (“sawah”), across locations and varieties. An integration of available farm manures with mineral fertilizer resulted in significant increases in paddy grain yield across locations, thus reducing the over reliance of famers on mineral fertilizers to improve soil fertility. From a significant initial increase (from less than 1.0 t ha -1 to over 4.5 t ha -1 ), mean paddy grain yield under the “Sawah” system consistently and continuously increased annually and currently stands at over 6.0 t ha -1 among farmer groups. Mean net income generated per hector under the “sawah” system also ranged from US $1,500 to US $2,800 over the same period among farmer-groups. There was also a gradual build up of total carbon and exchangeable bases (K, Ca, Mg) leading to improved nutrient levels, even though there was a net loss of both total Nitrogen and available Phosphorus over the same period. Ghana (possibly West Africa) has the potential to increase local rice production by over 300% when the “Sawah” system is adopted. Key words: Lowlands, improvement, rice yields, sawah system, soil productivity.

Influence of Drip Fertigation on Growth and Yield of Rice Varieties (Oryza sativa L.)

Field experiment was conducted at Central farm, Agricultural College and Research Institute, Madurai, during rabi 2009 - 2010 to study the Influence of drip fertigation on the growth and yield of rice varieties (Oryza sativa L.). Drip irrigation was scheduled once in three days and fertigation was given once in six days as per the treatment schedule. Observations on growth, yield attributes and yield of rice were recorded. Drip irrigation at 150 per cent PE+ drip fertigation of 100 per cent (RDF)+ azophosmet + humic acid recorded 19 per cent increased yield as compared to drip irrigation at 125 per cent PE+100 per cent RDF through drip. The increase in rice grain yield with drip irrigation at 150 per cent PE+ drip fertigation of 100 per cent RDF + azophosmet + humic acid was mainly attributed by greater and consistent availability of soil moisture and nutrients which resulted in better crop growth, yield components and ultimately reflected on the grain yield.

Cytokinin‐mediated source/sink modifications improve drought tolerance and increase grain yield in rice under water‐stress

Drought is the major environmental factor limiting crop productivity worldwide. We hypothesized that it is possible to enhance drought tolerance by delaying stress-induced senescence through the stress-induced synthesis of cytokinins in crop-plants. We generated transgenic rice (Oryza sativa) plants expressing an isopentenyltransferase (IPT) gene driven by P(SARK) , a stress- and maturation-induced promoter. Plants were tested for drought tolerance at two yield-sensitive developmental stages: pre- and post-anthesis. Under both treatments, the transgenic rice plants exhibited delayed response to stress with significantly higher grain yield (GY) when compared to wild-type plants. Gene expression analysis revealed a significant shift in expression of hormone-associated genes in the transgenic plants. During water-stress (WS), P(SARK)::IPT plants displayed increased expression of brassinosteroid-related genes and repression of jasmonate-related genes. Changes in hormone homeostasis were associated with resource(s) mobilization during stress. The transgenic plants displayed differential expression of genes encoding enzymes associated with hormone synthesis and hormone-regulated pathways. These changes and associated hormonal crosstalk resulted in the modification of source/sink relationships and a stronger sink capacity of the P(SARK)::IPT plants during WS. As a result, the transgenic plants had higher GY with improved quality (nutrients and starch content).